Labyrinth The secret of the Holy Grail is sought in this two-part miniseries set in modern-day and medieval France; John Hurt and "Downton Abbey's" Jessica Brown Findlay star. 8 p.m. KTLA; concludes Fri.

Greatest Mysteries: Louvre Explore the history of the storied museum in Paris, France, in this new special. 9 p.m. Travel